1. Field of the Invention
The invention relates to a synchronization device, and more particularly to a synchronization device for audio/video signals.
2. Description of the Related Art
In a digital broadcast application, audio/video synchronization is important. A transmission terminal transmits a bit stream to a receipt terminal. The bit stream comprises a packetized elementary stream (PES), a transport stream (TS), and a program stream (PS). A program clock reference (PCR) included in the TS is used for building the system time clock (STC) of the receipt terminal. A presentation time stamp (PTS), included in the PES, allows the receipt terminal to identify the play time of the PES. However, there may be a slight difference between the STC of the transmission terminal and the STC of the receipt terminal. Specifically, the STC difference increases as time required for the transmission to be completed increases. Thus, an output buffer of the receipt terminal operates at an overflow or under-run state.
In a general audio/video synchronization mechanism, the receipt terminal compares its own STC with a received PTS. The comparison and resulting difference allows the audio/video synchronization mechanism to determine whether the play time is running behind or ahead of schedule. When the play time is running behind schedule, the receipt terminal stops playing the audio/video. When the play time is running ahead of schedule, some data packets in the output buffer are dropped. However, due to the stoppage by the receipt terminal and dropping of data packets, noticeable breaks in images or sounds may be observed by users.
Thus, it is desired to provide a synchronization device and method for audio/video signals, wherein audio/video playing is not stopped or data packets are not dropped.